Switch drum for starting and controlling electromotors



.Nbv. 13,1923

L. sci-16M I SWITCH DRUM FOR STARTING AND CONTROLLING ELECTROMOTORSFiled Sent. 26, 1922 Patented Nov. 13, 1923.

UNITED STATES 1,474,094 PATENT OFFICE.

LUDWIG soHoN, or

ESSEN, GERMANY, ASSIGNOR TO FRIED. KRUPP AK'IIENGESELL- SCHAFT, 0F ESSEN-ON-TI-IE-RUHB, GERMANY.

SWITCH DRUM FOR STARTING AND CONTROLLING ELECTROMOTORS.

Application filed September 26, 1922. Serial No. 590,710.

[0 aZZ whom if; may concern:

Be it known that I, Loo'wre SoHoN, residing at Essen. Germany, a citizenof the German Republic, have invented a certain new and usefulImprovement in,Switch Drums for Starting and Controlling Electromotors,of which the following is a specification.

This invention relates to improvements in switch drums for starting andcontrolling electromotors and has for its object to provide the switchdrum with a device by means of which the drum can be locked in such amanner that an abnormally rapid return of the drum to a lower switchstep is rendered impossible and that any inadmissibly high stress on thecontacts designed to close or break the motor circuit is securelyavoided.

The subject matter of the invention is of particular importance inconnection with switch drums of the kind in which the motor circuit isnot interrupted at the contact members of the switch drum itself but atan auxiliary electromagnetic cut-out situated outside the switchdrum.This means that the device according to the invention is likewiseadapted for use in cases in which it is held desirable to lock the drumalso in the driving positions or solely in the same. while without theuse of such an auxiliary cut-out the switch drum can only be locked inits braking positions.

The accompanying drawing diagrammati-- cally illustrates, as anembodiment of the subject matter of the invention in connection with thewiring diagram of a D. C. t *amcar motor, a controller which cooperateswith an auxiliary electromagnetic cut-out serving to interrupt the motorcircuit and which is automatically locked as long as the motor currentexceeds a predetermined maximum value.

Referring now to the drawing. A designates the overhead line which isconnected to the positive pole ot a source of direct current and towhich is connected by means of a trolley 13 a line C leading to theground (negative pole). Placed in the line C so as to be connected inseries with one another and with the switch drum K when the latter is inits driving positions, are: the releasing coil. and the two breakforming contact pointsd and d of a circuit-breaker D provided forprotection of the plant against overload, a multi-step startingresistance E, the winding f of a magnet F that will still be furtherdescribed, the two break forming contact pointsg and g of the auxiliaryelectromagnetic cut-out G as well as the armature H and the excitingwinding H of the D. 0. motor to be controlled The overloadcircuit-breaker D contains, in addition, another magnet coil d whichacts on the same magnet core as the main current releasing coil (Z andwhich is wound in the same direction as the last mentioned coil. Themagnet coil (F is connected in parallel to the break (Z (Z and is of astrength such as to be able to hold the opened circuit-breaker D in itscut-out position contrary to the action of a spring coil 6Z constitutestherefore axholding coil. The auxiliary cut-out G possesses only onemagnet coil which is connected, on the one hand, to the contact point 9of the cut-out G and. on the other hand, to the outset of the first stepof the starting resistance E. Interposed between the coil 9 and thecontact point 9 is aresistance J by which any short-circuit is renderedimpossible when the auxiliary cut-out G is osed. The magnet coil isproportioned so that it will be able to overcome the force ot a spring 9counteracting the coil and open the cut-out Gr only in case itis putinto direct COHTflGClIlOn with the full voltage of the source of directcurrent. This is rendered possible by the intermediary of an auxiliaryswitch device which forms partc:! the controller and will therefore bede scribed in connection with the same.

The controller cooperating with the starting resistance consists oi? aswitch drum K provided i *ith contact bars and ot a regulating lever Kwhich constitutes the driving means for the drum and which is rotatableround the axis oi the switch drum for a slight angle with. relation tothe switch drum. l1} the drawing, the contact bars de signed to startand control the motor H H are mnittcd from the lower portion of theswitch drum lit the terminals of the corresponding wipers are indicatedby small cir cles 11 at which terminates the connecting tires leading tothe starting rcsistance'E,

the motor H H and the poles ol. the source of direct current. Theregulating lever K is mounted for tree rotation on the upper end taco Z1or the switch drum K by means of a pin 7 so as to he aljile to more withrelation to the switch drum between two stops and a which are likewisearranged on the end taco a at a small distance. The end face 71 ot theswitch drum K :turth e r carries a one-armed lever which is proi'idedwith a projection l1 adapted to en 'age a notch 7v oi the regulating:lcrer lll'ltltl the in'lluencc ot a spring if. \Vhei the i'egailatinnlever K is not handled, it forced by t he engagement oi? the project on76' with the notch Z to take a position midway hetween the two stops 70'and Z The regulating lever K possesses at its rear end an extensionenlarged so as to Form a sector 70 of :1 radius somewhat. larger thanthat. of the switch drum Kand having ttastened to its edge. in the.manner to he seen from the drawing, a metal rod 7x extemlino' parallelwith relation to the axis of the switch drum. The rod 70 constitutes acontact member which serves to cm'iduct ely connect, in the limitpositions ot the regulating lever K determinec by, the stops 70* and 70two oi" three slightly resilient contact members Z7. Z1 and 77 eachotwhich is arrange on one of three contact bars 70" to which are rivetedin parallel. radial planes to the switch drum K. The uppermost; contacthar 7'1 embraces approximately one halt and. the lowermost one 7d theother halt of the circumtercnce ot the switch drum. while theintermediate bar l embraces nearly the entire circumference. Thecooperating wipers 7a to 7r are arranged at a stationary por-- tion ofthe contr llcr casing in a manner such as to hear against a part of theswitch drum not covered hy the contact h rs when the switch drum K is inthe position shown, in which. it takes its Zero position with relationto the casino; (not shown). The intermediate contact memher 7r oi thethree contact memhers 70 to if is COllSi't'llClT-il and arranged so asto he touched by the rod 7r in each of the two limit positions oi the.reg"- ulating lever K. while the two other con tact memhcrs Z1 and arearranged so as to cause the rod Z? to engage the contact meinhcr oi" theuppermost contact bar 7c when the regulating lever touches the stop N.and to engage the contact memher Z of the lowermost contact bar I? whenthe regulating lerer touches the stop If. On account of the descrihedarrangement oi the contact hairs Z to 7r". the intern'lcdiate contacthar Ki will he in enminementwith the correspond- .in; wiper 7' in alloperative positions ol the switch drum K except for the zero-position.while the uppermost contact har i113 hetwcen the releasing coil /j" ofthe. auxiliary cut-out (:t and the series resistance .l. while the wiperis grounded through a line As will he re ilf. seen 'l'rom the drawin".the described :-1 witch connections will cause the magnet coil r to heput under the volt age of the direct current source every time. theregulating lever K will he returned 'lrom any one o! its ()llQl'tllQlYflpositions towards the zero-position, o l the switch drum K. so that now.in the driving positions ol' the switchv drum. the i of contact" memhersZ9 1 r and in the hralcin; positions the pair oi contact members if. lwill he hride'cd hr the. metal rod a.

The switch drum K carries at its upper end a ring-rtector-shapeilextension Z? the margin of which is provided with a series o'l teeth 7ccorres ionding in number to the number of driving. steps. The margin ofthe sector-shaped rearward extension 70 0'! the regulating lever k islikewise provided with teeth 0 which, however, are arranged more closelyto each other than the teeth Zr and are directed oppositely to thelatter. The toothed portions 7: and Xi thus form parts oi two oppositelydirected locking mechanisms which act each in one single direction andthe cooperating parts oi which are tor-med by two pawls P and Qinfluenced by the magnet F 7. already mentioned. The pawl P is pivotallyand resiliently connected to one arm P of a wrought iron hell cranklever P P which mounted on the casing of the controller K K and theother arm P of which has a thickened end 22" facing one ot the end Facesot' the magnet core F. The. pawl Q which is directed oppositely andmounted tor swinging motion in a plane parallel to the pawl P issimilarly pivoted to one arm (Q of another hell crank lerer Q Q theother arm Q of which has its thickened end of facing the other end faceoi. the magnet core F. The two thickened ends 7) and 7 form armatures otthe magnet l i'\ compression spring-1' R engaging hoth the le- Vcr armsP and Q tends to hold the ends p and apart from the end faces of thema"- net 1*. The stroke oi the two lever arms and Q pressed outwards hythe spring R, is limited by two fixed stops P" and Q? in such a positionthat the pawls P and Q are out of en jag'emcnt with the correspondingteeth 70? and 70 The magnetic conditionsht the douhle looking (lOVicO l7. P 0, Q 70 are proportioned. so that. in case the strength oi themotor current flowing avens;

tation of the regulating lever K and the switch drum K, either one orthe other of the two single acting locking devices P k and Q will causea locking of the controller K K A locking of the controller cantherefore takeplace in the driving positions as well as in the brakingpositions of the switch drum. Both locking devices will, however, becomeinoperative as soon as the motor current drops below the determinedmaximum value or the motor circuit is interrupted. In this case, thecontroller is free to be rotated in both directions of rotation.

With the end of describing the operation of the device set forth, it isassumed that all parts take the position illustrated in the drawing inwhich, more particularly, the regulating lever K of the controller K Ktakes the position in the middle between the stops k and 70 and theswitch drum K is in its zero-position, so that the motor circuit and thecircuit of the auxiliary switch device containing the contact members 70to 70 is interrupted at the switch drum and the magnet coils cl, g and fare currentless. The cut-outs I) and G are therefore closed and the twolocking devices P 70 and Q, is are inoperative. r

If the motor H H should be started, the controller K K has to be broughtfirst intothe position corresponding to the first driving step, thisbeing effected by rotating the regulating lever K in the direction ofthe arrow m. This movement will cause the projection 70 to be disengagedfrom the notch k and the regulating lever K to become engaged with thestop 70 while the switch drum is still. at rest. In this position, themetal rod 70 will establish a conductive connection between the contactmembers k and 7:" and, consequently, between the contact bars 76 and 70but the circuit con taining the contact members 7.1 to is will stillremain broken at the wipers 70 to 7.1 In continuing the rotation of theregulating lever theswitch drum K will likewise be moved in thedirection of the arrow m and the motor circuit will close now in awellknown manner through the resistance steps oi the starting resistanceE and the wipers indicated by the terminals Z! as well as through themain current contact bars (not shown) ot' the switch drum K. At the samelllll'lG lllfle wipers 7c and 70 will enter into touch with thecorresponding contact bars 70 and 7' of the auxiliary switch device,while a contact between the wiper k and the contact bark does not takeplace owing to the peculiar construction of this contact bar. Therefore,no circuit will as yet be closed through the contact members is. i

70 and the rod k, and the lineslVI, N will even remain currentless whenthe SWl ECh drunr further rotated n the direction ot a directionopposite to the arrow 0:, the

switch drum K will at first remain at rest and the metal rod 70 willcome into touch with the contact members 7c and 70 will cause thecircuit-l-A. B C (Z (Z (Z M 70 70 72 k 72 is N C-to be closed so thatthe magnet coil 9 will be under the full voltage and open the auxiliarycutout G. However, a certain although short time, known as switch-lag,will pass between the moment the said circuit is; closed and the momentat which the break of the motor circuit is terminated, this lag beingdue to the mechanical inertia of the cut-out G, the magnetic inertia ofits magnet coil 9'' and the inductive resistances existing in the maincircuit. According to experience, this switch-lag is mostly considerablylonger than the time that is necessary, in switching by jerks, formoving the controller into the position corresponding to the next lowerswitch step. In order to prevent injurious arc-forniations at the maincurrent contact members of the controller, provision has therefore to bemade for allowing a returning of the switch drum K from a higher to alower switch step only after the motor current has disappeared or at'least not sooner than the motor current has dropped below thepredetermined maximum value. This is automatically obtained by the intermediary of the electromagnetic locking device F 7, P P 72 For as longas the current flowing through the coil 7 still exceeds the admissiblemaximum value, the

This

magnet armature p as well asthe magnet armature are attracted and. thepawl P is held in engagement with the teeth 0 so that a rotation of theswitch drum opposite to the direction of the arrow :20, that is, towards its zero-position, is rendered .nnpossible. As Wlll. be evldentfrom what has been said, a further movement of the switch drum K in thesaid direction can. only take place when thestrength of current in themotoucircuit has dropped below the said maximum value. soon as thistakes place, the power of the spring R will overcome that of the magnetF 7 so that; the pawl P again placed out oi engagement with the teeth laIn the said positions of l the switch drum the likewise attracted magnetarmature 9* does not execute any locking action, since the teeth Z1 arenot in reach of the pawl The described device will operate entirelysimilarly when using the controllerK K- for braking electrically, inwhich case the motor-If! H operates as generator on the startingresistance It througl'l the auxiliar cut-out G and the magnet coil f. Itthe controller should be returned from a position which corresponds to astrong braking, lo a lower braking step, the regulating lever K whichhad been moved. opposite to the direction of the arrow rotor institutingthe braking llltlOll, must be turned back in the direction o'l the arrowrt'.-- This movement is. however, automatically rendered. impossible bythe locking device F fl, Q (2?, X1 until the motor current has droppedbelow the predeterulined inaxin'iuni value. As. long as the motorcurrent: still exceeds this maximum value the force of the magnet 1 fovercomes that of the spring R and the armature j renniins attracted andthe pawl. Q? engaged with the, teeth As long as the locking device ll 7,Q 71: Opera'- tive, the narrow pitch chosen -for the teeth Z7 will notallow the regulating lever K to approach to the stop to such an extentthat the rod 70 will abut against the contact members 0 h and thus closethe circuit containing the contact members Z1 to is.

The re ulatin lever K may. at the most C R) o I 3 move with relation tothe pawl Q by a fraction of the pitch of the teeth Z11 it the pawl Q isnot just opposite to a tooth space. The controller is therefore forcedto remain in the switch step once set untilthe braking current hasdropped below the predetermined maximum value. ills soon as this occurs,the magnet F 7 will release the armature and the pawl Q will again comeout of engagement with the teeth Z0 under the influence of the springThe main advantage of the described device resides in the :tact that anabnormally rapid returning ot the controller is rendered impossible indriving as well as in braking, thereby securely avoiding onerous andinjurious arc-formations at the main current contact members of theswitch drum and at the auxiliary cutout Gr. A special advantage of thedescribed locking device resides in the fact that the driver, whenproperly handling the controller, does not at all become aware of thelocking device which will only enter into action when the switchingoperations are executed at an improperly high speed.

Without changing the spirit ot the invention, one ot the lockingdevices, such as P M, may be omitted and one may restrict oneself toprotect the controller K K and the auxiliary cutout againstarc-'lm'mation only in braking electrically. In this case. for example,it it is intended to lock the controller electromagnetically inthebraking positions but not in the driving positions, the auxiliary cutoutG r might also be dispensed with and the regulating lever K rigidlycoupled with "the switch drum K.

Hmvever the use ofa double locking device 11 i'moei and ol? theauxiliary cut-out alliord the guarantee thatcven the slightestiiriulrious arc formation is kept away from the. Controller.

If the controller should not he used at all or only exceptionally forelectrical braldngthe electric connections can be changeih withoutdeparting from the nature ot the invention in. such a manner that theauxiliary cutout G' is only made use o'l in driving and not in braking.In this case, one oi the threev contact bars of the auxiliary switchdevice at the switch drum and the corresponding wiper can be dispensedwith. This embodiment atlords the further advan tage that the overloadcircuit breaker D can then be used as auxiliary cut-out instead oi". theauxiliary cut-out G, this being rendered possible by connecting theholding coil (Z o l the breaker D with the auxiliary cut-out in such amanner that it may serve at the same time as releasing coil.

Finally, it must be remarked that the magnet coil f can also becomecurrentless by releasing the main current coil (Z ot the overloadcircuitbreaker D. In such case. however the driver can restore the maincircuit only when he has returned the controller into its zero-positionand thus broken the main circuit also at the switch drum. thereby makingthe holding coil d currentless. The motor and the controller are thusprotected from injuries by abnormal strengths of current.

Claims:

1. The combination with a switch drum for starting and controllingmotors, comprising a driving member for said drum. ol a single actingmagnetic locking device tor preventing said driving member from returnmovement, said device being kept in its loch-- ing position by thearmature current of the. motor to be controlled when exceeding apredetermined value. said locking devi -e comprising magnet to beenergized by said armature current and two cooperative elements, one ofthese elements being termed by said driving member and the otherelementbeing placed under the influence ol said magnet.

2. The combination with a switch drum for starting and controllingmotors comprising a. regulating lever mounted to rotate freely withrelation to the switch drum for a small angle and an auxiliary switchdevice adapted to actuate a cut-out arranged in the motor circuit at apoint outside the controller upon returning the regulating lever fromany of its driving or braking pos ions. of a single actingelectromagnetic locking device including a magnet ada ted to heenergized by the armature current oi the motor to be controlled and twocooperative elements, one of these elements being formed by theregulating lever o l? the switch drum and the other element being placedunder the influence of the said magnet, and another single actingelectromagnetic locking device arranged oppositely to the firstmentioned locking device and, including also two cooperative elementsone of these elemnts being formed by the switch drum and the otherelement being likewise placed under the influence of the said magnet. e

3. The combination with a switch drum for starting and controllingmotors comprising regulating leveryof two single acting electromagneticlocking devices, an

auxiliary cut-out arranged in the motor circuit at a point outside thecontroller, and an auxiliary switch device for cooperation with theswitch drum and for causing the auxiliary cut-out to enter into actiononly upon moving the said regulating lever back from any of its drivingpositions.

The foregoing specification signed at Essen, Germany, this 4th day ofSeptember, 1922.

LUDWIG SCHGN.

